This invention pertains to compositions and therapeutic methods for reducing the craving for nicotine and for smoking cessation. More particularly, this invention is directed to improved compositions of nicotine lozenges and therapeutic methods to provide periodic doses of nicotine to persons who are attempting to quit smoking.
Nicotine replacement therapy as an aid to quitting smoking has been become increasingly popular. Nicotine chewing gum (nicotine polacrilex) and transdermal nicotine are two of the more popular forms of nicotine replacement available commercially. It has become clear, however, that the mere replacement of cigarettes with another nicotine source may not be sufficient to insure success in smoking cessation therapy. Specifically, conventional nicotine replacement therapy does not adequately address the symptoms associated with the cessation of smoking.
Of the many smoking withdrawal symptoms, craving for cigarettes is one of the most difficult to alleviate. As described in Steuer, J. D. and Wewers, M. E. in Oncology Nursing Forum 1989, 16, 193-198, cigarette craving is one of the most consistent, most severe, and earliest withdrawal symptoms experienced by those attempting to quit smoking. Some reports suggest that craving peaks over the first 24 to 72 hours of abstinence and then declines, although craving has been reported after five years of abstinence.
Research is focusing on the factors that precipitate craving in an attempt to better understand and deal with the problem of relapse. Some investigators believe that certain smokers are much more likely than others to experience craving symptoms, especially when trying to quit smoking. Based on literature reports and his own investigations, Harrington (in Br. J. Soc. Clin. Psychol. 1978, 17, 363-371) reported that smokers can be separated by craving versus noncraving status, and that these separate populations have different responses to smoking cessation therapy. (In his study, treatment consisted of various behavioral strategies, and nicotine replacement was not used.) In particular, abstinence during treatment and success at the end of treatment were significantly related to being a noncraver.
Most commercially available products for nicotine replacement in smoking cessation therapy have not specifically addressed the issue of satisfying craving for nicotine. Instead, as mentioned above, they have generally been targeted towards providing a stable baseline level of nicotine in the blood. Some evidence indicates that low consistent blood levels of nicotine (as provided by transdermal nicotine, and to a lesser extent by nicotine gum) relieve some of the symptoms of nicotine withdrawal, but craving symptoms may not be among these (see Russell, M. A. H. in Nicotine Replacement: a Critical Evaluation; Pomerleau, O. F. and Pomerleau, C. S., Eds.; Alan R. Liss, Inc.: New York, 1988; pp 63-94). This may be because cigarette smoking provides an initial sharp rise in blood level, which is missing in these nicotine replacement therapies. The blood level peak produced by cigarettes is both higher (between 30-40 ng/mL) and sharper (this peak is attained within 10 minutes) than the steadier levels obtained from gum or a transdermal system. Russell states that the optimal steady-state blood level for nicotine replacement is between 10-15 ng/mL, but that quick-rise effects are probably necessary for more complete relief from craving in the early stages of cigarette withdrawal. His investigations have indicated that a rise in nicotine blood level of at least 10 ng/mL in 10 minutes is required to obtain postsynaptic effects at nicotinic cholinergic receptors in the central nervous system and at autonomic ganglia. These postsynaptic effects may be responsible for drug-like "high" feelings such as lightheadedness or dizziness experienced by cigarette smokers.
As mentioned above, nicotine gum (nicotine polacrilex) is one of the commercially available sources of nicotine for replacement therapy. Nicotine gum is actually an ion-exchange resin that releases nicotine slowly when the patient chews, and the nicotine present in the mouth is delivered directly to the systemic circulation by buccal absorption. However, much of the nicotine is retained in the gum through incomplete chewing or is largely wasted through swallowing, so that the systemic bioavailability of nicotine from gum is low and averages only 30-40%. Moreover, compared with cigarette smoking, nicotine gum is a slow and inefficient source of nicotine.
Nicotine replacement through transdermal nicotine systems is another therapy that has become commercially available. These nicotine patches provide a low, consistent blood level of nicotine to the user, and bypass the first pass effects of the gut and liver. Transdermal nicotine systems can be designed to provide higher steady-state blood levels of nicotine, but are unable to provide blood level peaks or to provide a rapid increase in blood level. Thus both nicotine gum and transdermal nicotine compete with each other as products providing steady-state nicotine blood levels, but do not satisfy craving symptoms for cigarettes in some smokers.
Other nicotine replacement products that are on the market or have been proposed in the literature have not been of serious interest in smoking cessation therapy, because of problems related to their use, and also because of limited ability to satisfy craving for cigarettes. Nicotine vapor has been delivered to patients in aerosol form, similar to the inhaler technology used to supply bronchial asthma medications, and in a "smokeless cigarette" such as that marketed by Advanced Tobacco Products under the trade name Favor.RTM.. Some data indicate, however, that these modes of nicotine delivery do not result in significant nicotine blood levels in patients after use. In addition, inhalation of these nicotine vapor products may be too irritating to the mucosa to be tolerable by patients.
Another smokeless version of nicotine delivered to the buccal mucosa is provided by chewing tobacco, oral snuff, or tobacco sachets. Tobacco sachets, which are especially popular in Scandinavia and the U.S., contain ground tobacco in packets that are sucked or held in the mouth. However, as shown in FIG. (cigarette, nicotine gum, and tobacco sachet levels from Russell, M. A. H., Jarvis, M. J., et al. Lancet 1985, 2 1370), use of tobacco sachets results in nicotine blood levels that are more comparable to those resulting from nicotine gum use than from those resulting from cigarette smoking; i.e. they require approximately 30 minutes of use to attain the maximum level of approximately 12 ng/mL, which is less than half of the peak value from smoking one cigarette. One possible reason that nicotine from tobacco sachets is absorbed so slowly is that nicotine is released slowly into the mouth as with nicotine gum; another may be that a significant proportion of the nicotine is swallowed, and therefore subject to the first pass effect of the stomach and liver. In any case, these oral delivery forms may be useful for producing low, steady-state nicotine blood levels, but they do not provide the peak levels needed to satisfy craving.
The literature describes other capsules, tablets, and lozenges for oral delivery of nicotine. For example, WO 8803803 discloses a chewable capsule filled with a liquid containing 0.1-10.0 mg of nicotine, together with additives for improving flavor and dispersion. The capsules are provided in a variety of pH values to allow the patient a choice of nicotine absorption rate, and are especially intended as an aid to quitting smoking.
Another nicotine capsule formulation is disclosed by M. E. Jarvik et al. (in Clin. Pharm. Ther. 1970, 11, 574-576) for ingestion as a smoking cessation aid. These capsules, however, were apparently swallowed whole by the subjects, according to the theory that intestinal absorption of nicotine could produce significant blood levels. The study showed a small but significant decrease in the number of cigarettes smoked by subjects, but no quantitative measurements of nicotine blood levels were obtained.
The literature also describes different designs of tablets for delivering nicotine to the mouth and digestive system. BE 899037 discloses a tablet containing 0.1 to 5 mg nicotine as a base or water-soluble acid salt as an aid for quitting smoking.
Wesnes and Warburton (in Psychopharmacology 1984, 82, 147-150; and Psychopharmacology 1986, 89, 55-59) discuss the use of nicotine tablets in experiments examining the effects of nicotine on learning and information processing. In the first experiment, nicotine was added to dextrose tablets with a drop of tabasco sauce added to disguise the taste of nicotine. In the second experiment, nicotine was added to magnesium hydroxide tablets, under the theory that an alkaline environment in the mouth would enhance buccal absorption. Again, tabasco sauce was added to the tablets to mask the taste of nicotine in both active and placebo tablets. The subjects were instructed to hold the tablets in the mouth for 5 minutes before swallowing, in order to maximize contact with the buccal mucosa.
Shaw (for example in GB 2142822 and U.S. Pat. No. 4,806,356) describes a nicotine lozenge prepared from a mixture of inert filler material, a binder, and either pure nicotine or a nicotine-containing substance by cold compression. The lozenges are intended to be held in the mouth as they dissolve slowly and release nicotine gradually in the buccal cavity.
WO 9109599 describes a nicotine product for oral delivery in the form of an inclusion complex of nicotine and a cyclodextrin compound. The patent also discusses the use of various excipients and direct compression for manufacture of the product.
In recent years, several nicotine lozenges have been commercialized and are available as over-the-counter products in the U.K. Resolution.RTM. lozenges, manufactured by Phoenix Pharmaceuticals and distributed by Ernest Jackson, contain 0.5 mg nicotine, together with the anti-oxidant vitamins A, C, and E. Stoppers.RTM. lozenges, distributed by Charwell Pharmaceuticals Ltd., contain 0.5 mg nicotine and are available in chocolate, orange and peppermint flavors.
Since nicotine has an acrid, burning taste, these nicotine lozenges typically are formulated with sugar as a major component. However, weight gain after smoking cessation has been identified as a significant factor contributing to smoking relapse. According to a recent survey, current Smokers who had tried to quit were asked to judge the importance of several possible reasons for their return to smoking. Twenty-seven percent reported that "actual weight gain" was a "very important" or "somewhat important" reason why they resumed smoking: twenty-two percent said that "the possibility of gaining weight" was an important reason for their relapse. See The Health Benefits of Smoking Cessation: A Report of the Surgeon General, Executive Summary (1990). Thus, sugar-based nicotine lozenge formulations may be unacceptable for a smoking cessation program for those subjects concerned with weight gain.
To date, it has been difficult to deliver nicotine in a profile mimicking the nicotine blood levels achieved by consistent smoking, to satisfy cravings for nicotine in people who are attempting to quit smoking, and thus, to provide greater protection against relapse than other nicotine replacement therapies for people who are trying to quit smoking. It is therefore desirable to provide improved lozenge compositions and methods which avoid the disadvantages of these conventional nicotine delivery devices and methods while providing an effective means for delivering nicotine.